R1212D002A RICOH [RICOH electronics devices division], R1212D002A Datasheet - Page 13

• Manufacturer Part Number: R1212D002A
• Description: STEP-UP DC/DC CONTOLLER
• Manufacturer: RICOH [RICOH electronics devices division]

continuous. The continuous current through the inductor is described as Iconst, then,
follows:
and external components should be selected.
components is not included. The actual maximum output current is between 50% and 80% of the calculation.
Especially, when the IL
for V
In the continuous mode, the deviation of the current is equal between on time and off time.
Further, the electric power, P
When I
In this moment, the peak current, ILxmax flowing through the inductor and the driver Tr. is described as
With the formula 4,6, and ILxmax is,
Therefore, peak current is more than I
In the formula 7, peak current ILxmax at discontinuous mode can be calculated. Put Iconst=0 in the formula.
The explanation above is based on the ideal calculation, and the loss caused by L
OUT
, Vf (as much as 0.3V) of the diode should be considered.
OUT
I
I
ILx
ILx
V
OUT
OUT
IN
becomes more than formula 5, the current flows through the inductor, then the mode becomes
max
max
=
=
=
T
f
f
OSC
OSC
ON
=
=
L /
×
×
Iconst
V
X
V
V
OUT
=
is large, or V
IN
IN
(
2
2
V
/
V
×
×
OUT
+
IN
T
T
V
AV
ON
ON
×
−
IN
I
is equal to output electric power, V
2
2
×
OUT
V
/
/
IN
T
{
{
2
2
)
ON
+
IN
×
×
×
V
is low, the loss of V
L /
Toff
L
L
IN
OUT
×
×
..................................................................................... Formula 7
×
(
(
. Considering the value of ILxmax, the condition of input and output,
V
V
T
L /
ON
OUT
OUT
............................................................................. Formula 4
/(
−
−
2
V
V
×
IN
IN
) L
)
)
}
}
................................................................ Formula 8
+
=
V
V
IN
IN
IN
is generated with the on resistance of the switch. As
×
2
Iconst
×
T
ON
/(
OUT
/
2
V
×
× I
OUT
L
OUT
×
................................ Formula 6
V
, thus,
OUT
)
..................... Formula 5
X
switch and external
R1212D
13